1. Field of the Invention
The present invention relates to a continuous type ink jet recording apparatus which adjusts the viscosity of an ink liquid using a solvent supplied from a solvent cartridge, and more specifically to an ink jet recording apparatus having a function of detecting the emptiness of the solvent cartridge.
2. Description of Related Art
An ink jet recording apparatus is used for printing characters or graphics on the surface of a workpiece (JP 2007-190724 A). The ink jet recording apparatus is generally called “ink jet printer”. The ink jet printer includes a head which is placed above a manufacturing line and a controller body which supplies ink to the head. The ink jet printer charges an ink liquid and forms the ink liquid into droplets, and deflects the ink droplets to thereby perform printing on the surface of a workpiece.
In the ink jet recording apparatus disclosed in JP 2007-190724 A, the ink liquid is continuously supplied to the head even when ink droplets are not printed on a workpiece and the supplied ink liquid is collected through a gutter as an ink receiver. That is, the ink jet recording apparatus disclosed in JP 2007-190724 A is a continuous type ink jet printer.
As a method for replenishing an ink jet recording apparatus with an ink or solvent, there are employed many methods in which a reserve tank is installed in an ink jet recording apparatus (JP 2007-190724 A). However, in the methods in which a reserve tank is installed in an ink jet recording apparatus, filling the reserve tank with ink may cause contamination of the surroundings of the reserve tank. In view of such a circumstance, an ink jet recording apparatus that employs a cartridge system using a cartridge which can be attached to and detached from the ink jet recording apparatus has come to be available (JP 2011-500353 W).
When the cartridge system is employed, there may be employed a system which maintains the internal pressure of a cartridge at atmospheric pressure when sucking out a liquid inside the cartridge by a pump, or a negative pressure system which sucks out a liquid from a cartridge in a sealed state. JP 2011-500353 W employs the latter system, that is, the system which sucks out a liquid from a cartridge in a sealed state. In the negative pressure system, the internal pressure of the cartridge becomes a negative pressure by sucking out the liquid from the cartridge.
When the cartridge system is employed, it is necessary to detect that a cartridge mounted therein has become empty in order to perform accurate cartridge replacement. In order to achieve this object, an ink jet printer disclosed in JP 2011-500353 W includes a pump which is placed inside a main body thereof, that is, a pump for sucking out a liquid inside a cartridge. A pressure sensor which is placed on a tube path between the pump and the cartridge detects whether the cartridge has become empty.
According to the description in JP 2011-500353 W, when the volume of the cartridge becomes almost zero, the pressure in the tube path rapidly decreases. It is possible to confirm that the cartridge has become empty using this phenomenon.
When employing, for example, the method disclosed in JP 2011-500353 W, that is, the method which measures the pressure in the tube path which communicates with the cartridge as means for confirming the emptiness of the cartridge, the pressure in the tube path and the remaining amount in the cartridge therefore do not necessarily correspond to each other because the method is an indirect method. A container for storing liquid, the container constituting the cartridge, is crushed by suction performed by the pump and the volume thereof is reduced (volume reduction). The degree of crushability has an individual difference between containers more or less. Further, the pressure in the tube path changes depending on the individual difference. This fact shows that although the method of JP 2011-500353 W is effective to confirm that the cartridge has become almost empty, it is virtually not possible to more accurately detect that the cartridge has actually become empty.